xref: /illumos-gate/usr/src/common/mpi/mplogic.c (revision f9fbec18)
1 /*
2  *  mplogic.c
3  *
4  *  Bitwise logical operations on MPI values
5  *
6  * ***** BEGIN LICENSE BLOCK *****
7  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
8  *
9  * The contents of this file are subject to the Mozilla Public License Version
10  * 1.1 (the "License"); you may not use this file except in compliance with
11  * the License. You may obtain a copy of the License at
12  * http://www.mozilla.org/MPL/
13  *
14  * Software distributed under the License is distributed on an "AS IS" basis,
15  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
16  * for the specific language governing rights and limitations under the
17  * License.
18  *
19  * The Original Code is the MPI Arbitrary Precision Integer Arithmetic library.
20  *
21  * The Initial Developer of the Original Code is
22  * Michael J. Fromberger.
23  * Portions created by the Initial Developer are Copyright (C) 1998
24  * the Initial Developer. All Rights Reserved.
25  *
26  * Contributor(s):
27  *
28  * Alternatively, the contents of this file may be used under the terms of
29  * either the GNU General Public License Version 2 or later (the "GPL"), or
30  * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
31  * in which case the provisions of the GPL or the LGPL are applicable instead
32  * of those above. If you wish to allow use of your version of this file only
33  * under the terms of either the GPL or the LGPL, and not to allow others to
34  * use your version of this file under the terms of the MPL, indicate your
35  * decision by deleting the provisions above and replace them with the notice
36  * and other provisions required by the GPL or the LGPL. If you do not delete
37  * the provisions above, a recipient may use your version of this file under
38  * the terms of any one of the MPL, the GPL or the LGPL.
39  *
40  * ***** END LICENSE BLOCK ***** */
41 /*
42  * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
43  * Use is subject to license terms.
44  *
45  * Sun elects to use this software under the MPL license.
46  */
47 
48 #pragma ident	"%Z%%M%	%I%	%E% SMI"
49 
50 /* $Id: mplogic.c,v 1.15 2004/04/27 23:04:36 gerv%gerv.net Exp $ */
51 
52 #include "mpi-priv.h"
53 #include "mplogic.h"
54 
55 /* {{{ Lookup table for population count */
56 
57 static unsigned char bitc[] = {
58    0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4,
59    1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
60    1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
61    2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
62    1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
63    2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
64    2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
65    3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
66    1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
67    2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
68    2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
69    3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
70    2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
71    3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
72    3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
73    4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8
74 };
75 
76 /* }}} */
77 
78 /*
79   mpl_rsh(a, b, d)     - b = a >> d
80   mpl_lsh(a, b, d)     - b = a << d
81  */
82 
83 /* {{{ mpl_rsh(a, b, d) */
84 
mpl_rsh(const mp_int * a,mp_int * b,mp_digit d)85 mp_err mpl_rsh(const mp_int *a, mp_int *b, mp_digit d)
86 {
87   mp_err   res;
88 
89   ARGCHK(a != NULL && b != NULL, MP_BADARG);
90 
91   if((res = mp_copy(a, b)) != MP_OKAY)
92     return res;
93 
94   s_mp_div_2d(b, d);
95 
96   return MP_OKAY;
97 
98 } /* end mpl_rsh() */
99 
100 /* }}} */
101 
102 /* {{{ mpl_lsh(a, b, d) */
103 
mpl_lsh(const mp_int * a,mp_int * b,mp_digit d)104 mp_err mpl_lsh(const mp_int *a, mp_int *b, mp_digit d)
105 {
106   mp_err   res;
107 
108   ARGCHK(a != NULL && b != NULL, MP_BADARG);
109 
110   if((res = mp_copy(a, b)) != MP_OKAY)
111     return res;
112 
113   return s_mp_mul_2d(b, d);
114 
115 } /* end mpl_lsh() */
116 
117 /* }}} */
118 
119 /*------------------------------------------------------------------------*/
120 /*
121   mpl_set_bit
122 
123   Returns MP_OKAY or some error code.
124   Grows a if needed to set a bit to 1.
125  */
mpl_set_bit(mp_int * a,mp_size bitNum,mp_size value)126 mp_err mpl_set_bit(mp_int *a, mp_size bitNum, mp_size value)
127 {
128   mp_size      ix;
129   mp_err       rv;
130   mp_digit     mask;
131 
132   ARGCHK(a != NULL, MP_BADARG);
133 
134   ix = bitNum / MP_DIGIT_BIT;
135   if (ix + 1 > MP_USED(a)) {
136     rv = s_mp_pad(a, ix + 1);
137     if (rv != MP_OKAY)
138       return rv;
139   }
140 
141   bitNum = bitNum % MP_DIGIT_BIT;
142   mask = (mp_digit)1 << bitNum;
143   if (value)
144     MP_DIGIT(a,ix) |= mask;
145   else
146     MP_DIGIT(a,ix) &= ~mask;
147   s_mp_clamp(a);
148   return MP_OKAY;
149 }
150 
151 /*
152   mpl_get_bit
153 
154   returns 0 or 1 or some (negative) error code.
155  */
mpl_get_bit(const mp_int * a,mp_size bitNum)156 mp_err mpl_get_bit(const mp_int *a, mp_size bitNum)
157 {
158   mp_size      bit, ix;
159   mp_err       rv;
160 
161   ARGCHK(a != NULL, MP_BADARG);
162 
163   ix = bitNum / MP_DIGIT_BIT;
164   ARGCHK(ix <= MP_USED(a) - 1, MP_RANGE);
165 
166   bit   = bitNum % MP_DIGIT_BIT;
167   rv = (mp_err)(MP_DIGIT(a, ix) >> bit) & 1;
168   return rv;
169 }
170 
171 /*
172   mpl_get_bits
173   - Extracts numBits bits from a, where the least significant extracted bit
174   is bit lsbNum.  Returns a negative value if error occurs.
175   - Because sign bit is used to indicate error, maximum number of bits to
176   be returned is the lesser of (a) the number of bits in an mp_digit, or
177   (b) one less than the number of bits in an mp_err.
178   - lsbNum + numbits can be greater than the number of significant bits in
179   integer a, as long as bit lsbNum is in the high order digit of a.
180  */
mpl_get_bits(const mp_int * a,mp_size lsbNum,mp_size numBits)181 mp_err mpl_get_bits(const mp_int *a, mp_size lsbNum, mp_size numBits)
182 {
183   mp_size    rshift = (lsbNum % MP_DIGIT_BIT);
184   mp_size    lsWndx = (lsbNum / MP_DIGIT_BIT);
185   mp_digit * digit  = MP_DIGITS(a) + lsWndx;
186   mp_digit   mask   = ((1 << numBits) - 1);
187 
188   ARGCHK(numBits < CHAR_BIT * sizeof mask, MP_BADARG);
189   ARGCHK(MP_HOWMANY(lsbNum, MP_DIGIT_BIT) <= MP_USED(a), MP_RANGE);
190 
191   if ((numBits + lsbNum % MP_DIGIT_BIT <= MP_DIGIT_BIT) ||
192       (lsWndx + 1 >= MP_USED(a))) {
193     mask &= (digit[0] >> rshift);
194   } else {
195     mask &= ((digit[0] >> rshift) | (digit[1] << (MP_DIGIT_BIT - rshift)));
196   }
197   return (mp_err)mask;
198 }
199 
200 /*
201   mpl_significant_bits
202   returns number of significnant bits in abs(a).
203   returns 1 if value is zero.
204  */
mpl_significant_bits(const mp_int * a)205 mp_err mpl_significant_bits(const mp_int *a)
206 {
207   mp_err bits 	= 0;
208   int    ix;
209 
210   ARGCHK(a != NULL, MP_BADARG);
211 
212   ix = MP_USED(a);
213   for (ix = MP_USED(a); ix > 0; ) {
214     mp_digit d;
215     d = MP_DIGIT(a, --ix);
216     if (d) {
217       while (d) {
218 	++bits;
219 	d >>= 1;
220       }
221       break;
222     }
223   }
224   bits += ix * MP_DIGIT_BIT;
225   if (!bits)
226     bits = 1;
227   return bits;
228 }
229 
230 /*------------------------------------------------------------------------*/
231 /* HERE THERE BE DRAGONS                                                  */
232